The present invention generally relates to a rotary compressor to be used for an air conditioner or the like for an automobile.
Generally, as shown by the fuel saving cost competition of the automobiles in recent years, the vehicles are expected to be made lighter in weight. It is strongly desired that the compressors for air conditioning of the automobiles be reduced in weight. The engine room of the automobile has become narrower and narrower because of the increased compactness of design and so on of auxiliary appliances accompanied by exhaust gas regulation and performance improvement. The compressors for automobile air conditioning are gradually being converted from the conventional reciprocating motion type into a rotary type, which may be made smaller in size.
Generally, the rotary compressor is provided in a cast iron cylinder 1 having a cylindrical inner wall face as shown in FIG. 5. A plurality of radial slits 4 are provided in a steel rotor 2 which is offset from the cylinder center. A plurality of vanes 5 of aluminum series metal are engaged in the radial slits for free sliding operation therein. The rotor 2 is sealed in a vane chamber 6 within the cylinder by a front plate and a rear plate (not shown). A suction hole 8, a suction groove 9, and a discharge hole 10 are formed in the above described cylinder 1. A discharge valve 11 and a discharge valve cap plate 12 are mounted for closing the discharge hole 10 from the outside. It is to be noted that there are provided a cylinder head 13, a suction chamber 14, and a discharge chamber 15.
In the above described construction, when the rotor 2 clamped with the shaft 3 is rotated, the vanes 5 engaged with the rotor 2 are caused to slide due to back pressure and centrifugal force at the rear end portions thereof, and due to contact of the tip end portions thereof being depressed against the cylindrical inner wall face of the cylinder 1. In a volume increasing step of the vane chamber 6, a low temperature, low pressure refrigerant gas is caused to flow into the vane chamber 6 from the suction hole 8 and the suction groove 9 upon rotation of the rotor 2. In a volume reducing step, the refrigerant gas is compressed to a high temperature and high pressure. When the pressure rises to the discharge pressure, the discharge valve 11 opens, and the refrigerant gas flows out from the discharge hole 10 into the discharge chamber 15.
In such construction as described hereinabove, the compressor is very heavy, because the cylinder 1, the rotor 2 and the shaft 3 are made of an iron series metal. The reciprocating type compressors are mostly made of aluminum series metal. The rotary type of compressor is not superior in terms of weight. This is because, when the vanes of the aluminum series metal slide in contact with the cylindrical inner wall face of the cylinder and the radial slits of the rotor, abrasion is likely to be caused. For example, when the cylinder or the rotor is made of an aluminum series metal, abnormal abrasion or sintering is likely to be caused by the contact during the sliding operation, which reduces the durability and reliability. In order to prevent deformation due to the compression forces and high temperatures of the refrigerant gas, the cylinder and the rotor must be formed of materials with high strength. Thus, it is difficult to reduce the weight of the rotary compressor.